Process of producing cuprammonium cellulose articles



PROCESS OF PRODUCING CUPRAMMONEUM CELLULOSE ARTICLES Horst Fit-ind, Wuppertal-Langerfeld, Germany, assignor to J. P. Bemberg Aktiengesellschaft, Wuppertal-Oberbarmen, Germany No Drawing. Application May 7, 1957 Serial No. 657,502

Claims priority, application Germany May 11, 1956 Claims. (Cl. 18-54) This invention relates to an improved process for the production of cellulose articles such as filaments, fibers, threads, films, ribbons, tapes and the like, and more particularly, the invention relates to an improved process of producing filamentary to filmaceous cellulose materials from a cuprammonium cellulose spinning solution.

in the usual cuprammonium cellulose process, the cellulosic raw material is dissolved in an aqueous cuprammonium solution, the solution extruded or spun, e.g., as filaments or films, and the cellulose re-precipitated or coagulated by extrusion into a spin bath. monium solvent must consist of specific quantities or concentrations of copper (in cupric form) and ammonia in order for the cellulose to remain dissolved therein, and the aqueous spin bath, which may be acidic or basic, functions as a diluent to lower the concentration of ammemo. and copper to the point where the cellulose precipitates. The spin bath also serves to remove solvent from the precipitated filaments or films. Generally, when producing filaments or threads, the cuprammonium spinning solution is extruded into a funnel through which the spin bath is circulated, and the extruded and precipitated filaments are stretched as they pass through the funnel.

It is known that the tensile strength of the resulting cellulosic articles, such as films or fibers, can be increased by subjecting the so-called blue filaments leaving the funnel to a subsequent stretching or drawing. After stretching, the filaments or films are passed through a bath for washing and decopperizing. In order to further increase the tensile strength, the blue filaments leaving the funnel have been converted into a copper alkaline cellulose compound, and the filaments then stretched to a maximum of about 100% as they are passed through successive tartaric acid baths. In both of these methods, however, the filaments are stretched or drawn only after a substantially complete disintegration or separation of the cellulose from the cuprammonium'solution by water dilution and precipitation or coagulation of the cellulose. Even with the high stretch methods heretofore employed in which the filaments are gradually drawn in a coagulating or precipitating bath, the maximum tensile strengths which have been obtained are only about 2.5 grams per denier.

One object of the invention is to provide an improved process for the production of cellulose filaments and films having higher tensile strength and a denser structure than could be previously accomplished.

Another object of the invention is to provide a process of producing filamentary and filmaceous cellulosic articles of high tensile strength by a novel method of spinning or extruding a cuprammonium cellulose solution and stretching the coagulated product before regenerating the cellulose.

Still another object of the invention is to provide a new and improved method of setting or coagulating a cuprammonium cellulose solution extruded in the form of filaments or films.

The cupram- 2,930,671 Patented Mar. 29, 1960 These and other objects and advantages are more fully set forth in the following detailed description of the invention.

According to the invention, it has now been discovered that improved filaments and films having greater values of strength can be obtained in an unexpected and surprising manner by avoiding the usual disintegration, decomposition, precipitation, or separation of cellulose from the extruded cuprammonium cellulose solution until after the filaments or films have been stretched or drawn. The process of the invention is accomplished by setting or coagulating the extruded spinning solution without the usual precipitation or complete regeneration of cellulose therefrom in a novel aqueous spin bath, and stretching the extruded and coagulated spinning solution after having left the spin bath to obtain high values of tensile strength in the final product. Only after the cuprammonium cellulose spinning solution has been extruded, set, and stretched, is the cellulose separated or regenerated from the cuprammonium solution, preferably by a subsequent washing and decopperizing in an aqueous acid bath.

The novel aqueous spin bath of the invention contains three essential components as follows:

(1) A setting agent of an alkali metal salt or an alkaline earth metal salt, or mixtures thereof, in a concentration sufiicient to set or coagulate the extruded spinning solution;

(2) Up to about 8 mols/liter and preferably from about 2 to 6 mols/ liter of free ammonia; and

(3) An ammonia complex-forming metal salt.

The latter two components of the aqueous bath, i.e., the free ammonia and the ammonia complex-forming metal salt, should be present in a quantity or concentration 'sufiicient to prevent substantial separation or disintegration of cellulose from the extruded cuprammonium cellulose spinning solution in the spinning and stretching bath.

The cuprammonium cellulose spinning solution employed in the process of the invention can be prepared by well-known conventional method and preferably contains copper (in cupric form) in a concentration of from 2-4% and ammonia in a concentration of from about 4.5-7%. This spinning solution is extruded from a conventional spinning or casting head having an aperture or plurality of apertures to form the desired filament or film. For example, filaments can be spun from holes having a diameter of 1 mm. or less, preferably 0.1-0.3 mm. The spinning solution is extruded in the desired shape or form directly into the novel spinning and stretching bath having a composition as specified by the invention. Stretching or drawing of the extruded spinning solution after coagulation'in the novel bath is carried out in the usual manner, e.g., by means of a godet roller or similar drawing device.

The setting or coagulation of the cuprammonium cellulose solution is accomplished by the presence of the alkali metal or alkaline earth metal salts in the spin bath. The quantity or concentration of the setting agent or component (1) varies depending upon whether the alkali metal salts or the alkaline earth metal salts are employed. With alkali metal salts, a concentration of at least 2 mols/liter is preferably employed, and, alternatively, a concentration of at least 0.1 mol/liter of the alkaline earth metal is most advantageous.

Of course, the setting agent can, if desired, consist of a mixture of alkali and alkaline earth metal salts. In this case, however, the minimum concentration of the setting agent is preferably selected such that the sum of the concentrations, expressed as percentages of the above-mentioned minimum concentrations of each class of salts, is at least equal to (See Example III below, for example.) Thus, where a mixture of such salts is employed, the minimum concentrationis Obtained when the formula 100[a/2'+l2/0.1] isequal to at least 00, wherein a is the number of mols per liter of the alkali metal salt and'b is the number of mols per liter of the alkaline earth metal salt, based upon the'aqueous spin bath. I

As suitable alkali and alkaline earth metal salts, the following are especially useful: the halides, e.g., chlorides and bromides, nitrates, formates and acetates of sodium and potassium. If only alkali metal salts are employed, then the alkali sulfates and carbonates may also be used.

The optimum concentration of free ammonia, component (2), ofv the spin bath is that which corresponds or is about equal to the concentration of ammonia in the spinning solution, i.e., about 3 to 4 mols/liter. Many suitable ammonia complex-forming metal salts are known, and the following are especially useful as component (3) of the novel spin bath: the halides, e.g., chlorides and bromides, nitrates, formates and acetates of copper, zinc, cadmium, cobalt and nickel. In the absence of alkaline earth metal salts, the sulfates and carbonates of the same metals can be employed. The optimum concentration of such complexeforrning metal salts is obtained at a value of about 0.1 mol/iiter which corresponds to the concentration of the bivalent copper not bound to cellulose in the spinning solution. It will be readily understood that these salts will form complex ammonia compounds in the bath, and such combined or complex ammonia is not to be included within the quantities measured as component (2), designated herein as free ammonia.

While the setting agent, component (1), causes the extruded spinning solution to coagulate or set, the free ammonia and complex-forming metal salts, components (2) and (3), act to repress or substantially suppress the separation or disintegration of cellulose from the cuprammonium solution. The stretch capacity of the extruded filaments or films is at its maximum when the disintegration of the spinning solution, i.e., separation of cellulose from the cuprammonium solvent, is completely prevented. This state or-condition is substantially achieved when employing the above-mentioned optimum concentrations of components (2) and (3). Higher concentrations of these compounds in the spin bath is'pejrmissible, but no further improvement of the stretchingcapacity of the filaments or films can be achieved thereby. A

Although priorprocesses provide a stretching of only 30 to 40%, and at most 100%, after the usual extrusion and reprecipitation of cellulose in a simple aqueous bath diluent, the present invention permits the extruded filamentary to filmaceous materials to be stretched or'elongated to from 50% to as high as 350%. The structure of thefinished product isthereby made considerably more dense, and it is possible to achieve high values of tensile strength. For example, the invention is capable of providing filaments having dry tensile strength values of about 3 to 5 grams/denier and wet-strength values of about 2 to 4 grams/denier, together with a wet to dry elongation value of 5 to 12%, as well as films with a strength of kg./mm.

The following examples provide further specific illustration of the invention, but the invention is not restricted to these examples. 7 i Example I A cuprammonium cellulose solution having 9% cellulose, 6.5% ammonia and 3.8% of copper is spun through a nozzle of 0.1 mm. in diameter into a spin bath that contains 0.8 mol/liter of calcium chloride, 3.7 mols/liter of ammonia and 0.1 mol/ liter of copper chloride. The singlestrand filament is set or coagulated by the spin bath and is then subjected to a stretch or elongation of 150%. After washing and decopperizing with hydrochloric acid, a single-strand filament is obtained with a titer of 5 denier. Its properties are: dry strength, 5 .2 grams/denier; wet

. 4 strength, 4.4 grams/denier; dry'elongation, 8%; and wet elongation, 5%.

Example II Example III A spinning solution having the same composition as Example I is extruded through a 24-hole nozzle into a spin bath which contains 0.6 mol/ liter (600% of the minimum quantity) of calcium chloride, 1 moi/liter (50% of the minimum quantity) of sodium chloride (altogether 650%), 2 mols/liter of ammonia, and 0.1 mol/liter of copper chloride. Theset or solidified thread is stretched by and acidified with hydrochloric acid. The resuiting filamentary material has a titer of 60 denier, a dry elongation of 10%, and a Wet elongation of 8%. The dry tensile strength is 3.4 grams/denier, and the wet strength is 2.3 grams/denier.

Example 1V A spinning solution of the same composition as Example I is extruded through a l6-hole nozzle into a spin bath that contains 4 mols/liter of sodium chloride, 0.2 mol/liter of ammonia, and 0.01 moi/liter of copper sulfate. In a subsequent stretching of 50%, the following propertiesof the filamentary material are obtained: a titer of 40 denier; a dry strength of 3.2 grams/denier; a wet strength of 2.3 grams/denier; a dry elongation of 11%; and a wet elongation of 8%.

The invention is hereby claimed as follows:

1. In a process for the production of cellulose articles such as filaments and films from a cuprammonium cellulose spinning solution, the improvement which comprise: extruding a cuprammonium spinning solution in an aqueous spin bath which contains (1) a setting agent selected from at least one member of the group consisting of alkali metal and alkaline earth metal salts in a quantity sufficient to set the extruded spinning solution, (2) from 2 up to about 8 mols/liter of free ammonia, and (3) an ammonia complex-forming metal salt, said ammonia and said ammonia complex-forming metal salt being present in a quantity sulficient to prevent substantial separation of cellulose from the extruded cuprammonium cellulose spinning solution; and stretching the extruded and coagulated product prior to separating the cellulose therefrom.

2. An improved process as defined in claim 1 wherein the setting agent is an alkali metal salt dissolved in the aqueous spin bath'in an amount of at least 2 mols/liter.

3. An improved process as defined in claim 1 wherein the setting agent is an alkaline earth metal salt present in the aqueous spin bath in an amount of at least 0.1 mol/ liter.

4. An improved process as defined in claim 1 wherein the setting agent is a mixture of an alkali metal salt and an alkaline earth metal salt dissolved in the aqueous spin bath in an amount such that 100[a/2+b/0.1] equals at least 100 wherein a is the number of mols/liter of the alkali metal salt and b is the number of mols/ liter of the alkaline earth metal salt.

5. An improved process as defined in claim 1 wherein of ammonia in the cuprammonium cellulose spinning solution.

7. An improved process as defined in claim 1 wherein the setting agent is an alkali metal salt selected from the group consisting of alkali metal halides, nitrates, formates and acetates, sulfates and carbonates.

8. An improved process as defined in claim 1 wherein the alkaline earth metal salt is a member of the group consisting of alkaline earth metal halides, nitrates, formates and acetates.

9. An improved process as defined in claim 1 wherein the ammonia complex-forming metal salt is a member of the group consisting of the halides, nitrates, formates, acetates, sulfates and carbonates of copper, zinc, cadmium, cobalt and nickel in a concentration in the aqueous spin bath of up to about 0.1 mol/liter, and wherein the setting agent is an alkali metal salt.

10. An improved process as defined in claim 1 wherein the ammonia complex-forming metal salt is present in the aqueous spin bath in a molar concentration about equivalent to the corresponding molar concentration of the bivalent copper not bound to cellulose in the cuprammonium cellulose spinning solution.

11. An improved process as defined in claim 1 wherein the extruded and coagulated cuprammonium spinning solution is stretched after leaving the aqueous spin bath to from 50% to about 350%.

12. In a process for the production of filamentary and filmaceous regenerated cellulose materials from a cuprammonium cellulose spinning solution, the improvementwhich comprises: extruding a cuprammonium cellulose spinning solution into an aqueous spin bath which contains the components 1) a setting agent selected from at least one member of the group consisting of alkali metal salts and alkaline earth metal salts in a minimum concentration based upon the aqueous spin bath such that l00[a/2+b/ 0.l] equals at least 100 wherein a is the number of mols/liter of the alkali metal salt and b is the number of mols/liter of the alkaline earth metal salt,

(2) free ammonia in a concentration of from 2' up to about 8 mols/liter, and

(3) an ammonia complex-forming salt of a metal selected from the group consisting of copper, zinc, cadmi um, cobalt and nickel in a concentration of up to about 0.1 mol/liter,

component (1) being present in a quantity suflicient to coagulate the extruded spinning solution and components (2) and (3) being present in a quantity suflicient to prevent substantial separation of cellulose from the extruded spinning solution; stretching the extruded and coagulated spinning solution from 50 to 350% prior to separation of the cellulose therefrom; and washing and decopperizing the extruded, coagulated and stretched product in an acid aqueous bath to regenerate cellulose.

13. In a process for the production of filamentary and 6 filmaceous regenerated cellulose materials from a cupram monium cellulose spinning solution, the improvement which comprises: extruding a cuprammonium cellulose spinning solution into an aqueous spin bath which con tains in solution the components (1) a sodium salt in a minimum concentration of at least 2 mols/liter and sufficient to coagulate the extruded spinning solution,

(2) free ammonia in a concentration of about 2 to 6 mols per liter, and

(3) cupric chloride in a molar concentration about equivalent to the corresponding molar concentration of the bivalent copper not bound to cellulose in the cuprammonium cellulose spinning solution,

components (2) and (3) being present in a quantity sufficient to prevent substantial separation of cellulose from the extruded spinning solution in the spin bath; stretching the extruded and coagulated spinningsolution from to' 350% prior to separation of the cellulose therefrom; and washing and decopperizing the extruded,

coagulated and stretched product in an acid aqueous bath to regenerate cellulose.

14. In a processfor the production of filamentary and filmaceous regenerated cellulose materials from a cupramspinning solution into an aqueous spin bath which contains in solution the components (1) a sodium salt in a minimum concentration of at least 2 mols/literand sufiicient to coagulate the extruded spinning solution,

(2) free ammonia in a concentration of about 2 to 6 mols per liter, and v (3) ,cupric sulfate in a molar concentration about equivalent to the coresponding molar concentration of the bivalent copper not bound to cellulose in the cuprammonium cellulose spinning solution,

components (2) and (3) being present in a quantity sufficient to prevent substantial separation of cellulose from the extruded spinning solution in the spin bath; stretching the extruded and coagulated spinning solution from 50 to 350% prior to separation of the cellulose therefrom; and washing and decopperizing the extruded, coagulated and stretched product in an acid aqueous bath to regenerate cellulose. p

15. An improved process as defined in claim 1 wherein the ammonia complex-forming metal salt is a member of the group consisting of the halides, nitrates, formates, and acetates of copper, zinc, cadmium, cobalt, and nickel in a concentration in the aqueous spin bath of up to about 0.1 mol/liter, and wherein the setting agent is an alkaline earth metal salt.

References Cited; in the file of this patent UNITED STATES PATENTS 2,319,428 Mothwurf May 18, 1943 

1. IN A PROCESS FOR THE PRODUCTION OF CELLULOSE ARTICLES SUCH AS FILMENTS AND FILMS FROM A CUPRAMMONIUM CELLULOSE SPINNING SOLUTION, THE IMPROVEMENT WHICH COMPRISE: EXTRUDING A CUPRAMMONIUM SPINNING SOLUTION IN AN AQUEOUS SPIN BATH WHICH CONTAINS (1) A SETTING AGENT SELECTED FROM AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF ALKALI METAL AND ALKALINE EARTH METAL SALTS IN A QUANTITY SUFFICIENT TO SET THE EXTRUDED SPINNING SOLUTION, (2) FROM 2 UP TO ABOUT 8 MOLS/LITER OF FREE AMMONIA, AND (3) AN AMMONIA COMPLEX-FORMING METAL SALT, SAID AMMONIA AND SAID AMMONIA COMPLEX-FORMING METAL SALT BEING PRESENT IN A QUANTITY SUFFICIENT TO PREVENT SUBSTANTIAL SEPARATION OF CELLULOSE FROM THE EXTRUDED CUPRAMMONIUM CELLULOSE SPINNING SOLUTION, AND STRETCHING THE EXTRUDED AND COAGULATED PRODUCT PRIOR TO SEPARATING THE CELLULOSE THEREFROM. 